Flow Drill Screw Fastening Structure for Gap-Free Mating Faces

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Solution Overview

Problem

Existing fastening structures using flow drill screws often result in gaps between mating faces due to swarf extrusion during thread formation, which are not adequately addressed by previous solutions.

Innovation Solution

A fastening structure that incorporates clearance holes at the mating faces to extrude swarf generated during thread formation, with markers and counterbores to facilitate accurate screw positioning and stable fastening, preventing gaps between the co-fastened members.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a flow drill screw is used to fasten overlapped members together, then the members can be securely fastened, but swarf is extruded between mating faces causing gap formation

Engineering Contradiction:

Improvefastening strengthVSAvoidmating face flatness

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent extracts the harmful swarf from the mating face interface by providing a dedicated clearance hole that directs swarf extrusion away from the contact surface, preventing gap formation while maintaining the fastening function

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The clearance hole acts as an intermediary structure that mediates between the thread formation process and the mating faces, providing a controlled path for swarf extrusion that protects the mating face integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If a groove is formed in the outer face to reduce swarf generation, then some gap formation is suppressed, but the effect is insufficient

Engineering Contradiction:

Improvemating face flatnessVSAvoidstructure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent converts the harmful swarf extrusion into a beneficial controlled process by directing it into the clearance hole, transforming the problem of swarf generation into a solution that prevents mating face separation

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The clearance hole is pre-formed in the member before fastening, preparing a designated path for swarf extrusion in advance, which prevents gap formation during the subsequent thread formation process

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Effectively suppresses gap formation between mating faces by extruding swarf into clearance holes, ensuring precise alignment and stable fastening, while allowing for easy screw positioning and reduced risk of axial misalignment.

Implementation Method 1

a screw that utilizes frictional heat to bore a hole and form a thread

Methodology Applied

Scientific EffectFrictional heat: Friction

Implementation Method 2

Swarf generated as a result of thread formation by the screw is extruded into the clearance hole

Methodology Applied

Scientific EffectExtrusion: Extrusion

Data Source

PatentUS11473608B2Fastening structure and fastened structural body

Publication Date: 2022.10.18 TOYOTA JIDOSHA KK

AI summary

A fastening structure includes: plural overlapping co-fastened members, a clearance hole being formed at at least one mating face of mutual mating faces of the plural co-fastened members, and a screw utilizing frictional heat to bore a hole and form a thread, passing through the clearance hole, and fastening the plural co-fastened members together.